Vehicle floor heating device

ABSTRACT

A foot heating device for heating an occupant&#39;s feet on the floor of a motor vehicle. The device includes a panel having a bottom surface residing on the floor and a top surface that supports the occupant&#39;s feet. The panel also includes and insulating layer, a radiant barrier layer disposed adjacent to the insulating layer and a heating layer disposed between the radiant layer and the top surface. A heater is included in the heater layer. The heater is configured to provide heat for heating the top surface. A lower portion of the panel has a first thermal resistance and an upper portion of the panel has a second thermal resistance. The first thermal resistance being greater than the second thermal resistance.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention generally relates to automotive climate control, and, moreparticularly, to a foot warming device for use on a vehicle floor.

2. Background of the Invention

Many people have difficulties in keeping their feet warm while seated ina vehicle, particularly when cool temperatures at the floor levelprevail. Keeping the feet comfortably warm is difficult for a number ofreasons, including poor circulation to the feet.

The predominate technology for vehicle footwell or floor heating is thedistribution of engine waste heat from the heater core in an HVAC(Heating Ventilating and Air Conditioning) module. One problem with thistype of system is that the heater core is cold during cold starting ofthe vehicle and, accordingly, there is little to no waste heat. Anotherproblem is that, even when the heater core is warm and able to providewaste heat, the metal footwell substructure of the vehicle transfers asignificant portion of the heat to air outside of the vehicle duringcold weather, via thermal conduction through the metal substructure.

BRIEF SUMMARY OF THE INVENTION

In overcoming the drawbacks and limitations of the prior art, thepresent invention provides a new and improved device for heating avehicle occupant's feet.

In at least one embodiment, the present invention provides a floor baseddevice for heating an occupant's feet. The device includes a panelhaving a bottom surface that resides on the floor of the vehicle and atop surface that supports the occupant's feet. The panel furtherincludes an insulating layer, which may include or be the bottomsurface, a radiant barrier layer disposed adjacent to the insulatinglayer and a heater layer disposed between the radiant layer and the topsurface. The heating layer includes a heater that provides heat to thetop surface. A first thermal resistance is defined between the heaterand the bottom layer. A second thermal resistance, which is less thanthe first thermal resistance, is defined between the heater and the topsurface of the panel.

In at least one other embodiment of the present invention, the heatinglayer includes a plurality of channels and portions of the heater aredisposed along or within the channels.

Further objects, features and advantages of the invention will becomeapparent from consideration of the following description and theappended claims when taking in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heating device in accordance with anembodiment of the present invention;

FIG. 2 is an exploded perspective view of the heating device seen inFIG. 1;

FIG. 3 is a cross sectional view through a heating device in accordancewith an embodiment of the present invention;

FIG. 4 is a cross sectional view through a heating device in accordancewith another embodiment of the present invention;

FIG. 5 is a cross sectional view through a heating device in accordancewith a further embodiment of the present invention;

FIG. 6 is a cross sectional view through a heating device in accordancewith yet another embodiment of the present invention; and

FIG. 7 is a perspective view of a heating device in accordance withanother embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the present invention are disclosed herein. Itis understood, however, that the disclosed embodiments are merelyexemplary of the invention, which may be embodied in various andalternative forms. The figures are not necessarily to scale, somefigures may be exaggerated or minimized to show the details of aparticular component. Therefore, specific structural and functionaldetails disclosed herein are not to be interpreted as limiting, butmerely as a representative basis for the claims and for teaching oneskilled in the art to practice the present invention.

The present invention seeks to overcome some of the problems associatedwith heating a person's feet in a motor vehicle, including the problemsassociated with directing cold air from the HVAC module towards theoccupant's feet.

Applying the principles of the present invention, a heating device isprovided that rests on the vehicle floor and heats the occupant's feet.The heating device comprises a panel which includes a heating portion orheater. The heater is disposed within the panel and provides heat forheating the top surface of the device, where the occupant's feet aresupported. Heat provided by the heater may, for example, come fromheating elements disposed within the heater or from air that is heatedprior to being received by the panel.

The panel has a lower portion and an upper portion. The lower portion isdefined between the bottom surface of the panel and the heater. Theupper portion is defined between the heater and the top surface of thepanel. Both the upper and lower portions of the panel have a respectivethermal resistance. That is, the corresponding thickness of the portiondivided by the corresponding thermal conductivity of the portion defineseach portion's thermal resistance. A relatively high value for thermalresistance corresponds to a portion having high thermal insulativeproperties. Conversely, a relatively low value for thermal resistancecorresponds to a portion having low thermal insulative properties orhence, high thermal conductive properties.

The panel is constructed such that the lower portion has a higherthermal resistance than the upper portion. This construction provides athermal gradient bias for transferring heat from the heater upwardstowards the top surface of the panel. The greater the thermal resistanceof the lower portion is relative to the thermal resistance of the upperportion, the more thermally isolated the panel becomes from the floor ofthe vehicle. During cold weather, the metal of the footwell substructureis cold and transfers heat quickly to outside the vehicle. This resultsin significant heat loss. However, by thermally isolating the panel fromthe footwell, less heat is lost through the floor, while more heat isdirected towards the occupant's feet on the top surface of the device.

Referring now to the drawings, FIG. 1 generally illustrates a heatingdevice 10 for a vehicle 12, as embodied by the present invention. Theheating device 10 is located on a floor 14 of the vehicle 12 andsupports an occupant's feet 16, while also providing heat to theoccupant's feet 16.

The device 10, as seen in FIG. 2, includes a panel 18 having a bottomsurface 20 that rests on the floor 14 of the vehicle 12. The panel 18also has a top surface 22 on which the occupant's feet 16 with reside.Between the top and bottom surfaces 20, 22, the panel 18 includes aninsulating layer 24, a radiant barrier layer 26 and a heating layer 28.The bottom surface 20 may be a surface of the insulating layer 24, oranother layer. The radiant barrier layer 26 is disposed adjacent to theinsulating layer 24. The heating layer 28 is disposed between theradiant barrier layer 26 and the top surface 22 of the device 10. Whilethe top surface 22 may be a surface of the heating layer 28, thissurface 22 may optimally be part of a decorative layer 30 provided overthe heating layer 28.

Preferably, the decorative layer 30 is thin and disposed immediatelyadjacent to the heating layer 28. The decorative layer 30 may be forexample, carpet, wood veneer or any other suitable decorative materialthat is, preferably, more thermally conductive than the insulating layer24.

Referring to FIGS. 2-6, various embodiments of the device 10 areillustrated therein and like elements are being designated. In eachembodiment, the insulating layer 24 provides thermal insulation from thefloor 14. The insulating layer 24 may be made, for example, from a lowthermally conductive plastic material such as polypropylene (PP) or highdensity polyethylene (HDPE). In one construction, the device may have asthe insulating layer 24 a 2.5 mm thick layer of PP with a thermalconductivity of about 0.0023 J/(cm*sec*deg C) to provide a thermalresistance of about 100 (cm̂2*Sec*deg C)/J. Alternatively, the insulatinglayer 24 may have a composite structure where two or more materials,each having preferably low thermal conductivity, comprise the layer 24.For example, the insulating layer 24 may be made from co-extrudedplastic sheet that includes two or more different plastic materials. Onthe other hand, the insulating layer 24 may be made from a polymericmaterial including pockets (e.g. foam) or other volumes that containair. Air, having a thermal conductivity of about 0.00026 J/(cm*sec*degC), provides excellent insulative properties to the layer 24. Othersuitable materials with relatively low thermal conductivity, which areknown in the art, may also be used.

The insulating layer 24 may further include a rib arrangement (see FIGS.3-6) for supporting the panel 18 on the floor 14. The rib arrangement,having an open volume 39 defined between each pair of ribs 38 andcontaining air, has a relatively high thermal resistance that enhancesthermal isolation of the panel 18 from the floor 14. In one illustrativeconstruction, the insulating layer is made from PP, has a solid topportion 42 that is about 1-1.5 mm thick and from which extend ribs 38that are about 5-7 mm tall by 1-1.5 mm thick and spaced about 7-10 mmapart. The insulating layer 24 in this arrangement has a thermalresistance of at least about 1700 (cm̂2*Sec*deg C)/J.

The insulating layer 24 may further include protrusions (not shown) forgripping the floor 14 that are disposed along the bottom surface 20. Forexample, if the floor 14 of the vehicle 12 is covered with carpet, theprotrusions may be small nibs that penetrate into the pile of the carpetto provide a mechanical interlock that impedes side to side movement ofthe panel 18. Other known mechanisms for retaining floor panels couldalso be employed.

The radiant barrier layer 26 is provided so as to reflect radiant heattowards the top surface 22. The radiant barrier layer 26 is preferablymade from a low emissivity material, which may be thin and flexible,such as a metal foil or a metallized polymer film or sheet. Othersuitable thermally reflective materials may also be used. Moreover, theradiant barrier layer 26 may include openings to allow for directbonding or attachment of the insulating layer 24 to the heating layer28.

The heating layer 28 includes a heater 32, disposed within the heatinglayer 28 that is configured to provide heat for heating the top surface22.

As illustrated in FIGS. 3, 4 and 6, the heater 32 includes heatingelements 40 for providing heat. The heating elements 40 may be, forexample, electrical resistance heating elements or a heating foil. Inone embodiment and as illustrated in FIG. 3, the heating layer 28 hasheating elements 40 bonded to a thin upper sub-layer 44. The thin uppersub-layer 44 of the heating layer 28 may be a plastic film, such aspolyethyleneterepthalate (PET) or polyethyleneisopthalate (PEI), whichhas excellent temperature stability. Other suitable temperature stablematerials known in the art may also be used. The thin upper sub-layer 44may further be bonded, preferably to form a seal, to a lower sub-layer46 of the heating layer 28. The lower sub-layer 46 may be, for example,a PP sheet. Alternatively, the upper sub-layer 44 of the heating layer28 may be bonded to the radiant barrier layer 26 which, for example, mayhave the form of a metallized plastic sheet.

The device 10 may further include an ON-OFF switch 47 (provided on theinstrument panel of the vehicle 12) electrically coupled to the powersupply 48 of the vehicle 12 and to the heater 32 to form an electricalcircuit. The panel 18 may also include a thermostat 50 or a positivetemperature coefficient device, which is electrically coupled to thecircuit and which controls the heating elements 40 to within apredetermined temperature range. Alternatively, the heating elements 40may be positive temperature coefficient thermister heaters, which areself regulating to within a temperature range. Other suitable heatingelements know in the art may also be used.

The construction of the panel 18 defines a lower portion 34, extendingfrom beneath the heater 32 and includes the bottom surface 20. Thislower portion 34 has a first thermal resistance. An upper portion 36 ofthe panel 18, extending from the heating portion 32 to and including thetop surface 22 of the panel 18, has a second thermal resistance. Thethermal resistance of the lower portion 34 is greater than the thermalresistance of the upper portion 36 for the reasons previously discussed.In at least one embodiment, the thermal resistance of the upper portion36 is less than about 100 (cm̂2*Sec*deg C)/J. In another embodiment, theratio of the first thermal resistance to the second thermal resistanceis at least about 5 to 1 and in a preferred embodiment the ratio is atleast about 17 to 1.

Referring to FIGS. 4-7, the heater 32 may be configured as includingchannels 54 to receive and pass air through the heating layer 28 so asto provide heat to the top surface 22 by conduction through the panel 18and/or forced convection directed at the occupant's feet positioned onthe top surface 22. The air may be heated prior to being received, as inFIG. 5, or the air may be heated as it is advanced through the channels54 and along the heating elements 40, wherein both the channels andheating element are disposed within the heating layer 28. In at leastone embodiment, the heating layer 28 is in fluid communication with theHVAC system 52 (Shown in FIG. 1) of a vehicle 12. In such aconstruction, the heating layer 28 advances air received from the HVACsystem 52 along the channels 54 of the heater 32 and may discharge theheated air directly towards the occupant's feet 16 (Shown in FIG. 7).Whenever so provided, the channels 54 have inlet ends 58 that receivethe air from the HVAC system 52 and discharging ends 60 that dispensethe air. The panel 18 may further include a deflector 62 proximate thedischarging ends 60 and positioned such that the dispensing air isdirected towards the occupant's feet 16.

Referring to FIG. 6, the channels 54 of the heating layer 28 may be openat the bottom such that the radiant barrier layer 26 is exposed to thechannels 54 and directly reflects radiant heat back towards the topsurface 22. This arrangement is suitable both for when the heatingelements 40 are disposed within the heating portion 32 or when feed airis heated prior to being received by the panel 18. Alternatively, thebottom of the channels 54 may themselves be metallized to form theradiate barrier layer 26 therein.

A duct 64 interfacing with the HVAC system 52 and the heating layer 28provides fluid communication between the HVAC system 52 and the heatinglayer 28. In one possible construction, the duct 64 may have heatingelements disposed within the internal flow volume of the duct 64. Theseheating elements may be of the type previously discussed and beelectrically coupled to an HVAC controller (not shown) that controls theHVAC system 52, and the vehicle power supply 48 to form an electricalcircuit. When cool air from the HVAC system 54 is received within theduct 64, as may occur for example during a cold start of the vehicle 11,the positive temperature coefficient thermister heaters cooperating withthe controller, quickly warms the air to within a given temperaturerange. When warm air from the HVAC system 52 is subsequently receivedwithin the duct 64, the heaters would not heat the air. The warm air isthereafter received by the heating layer 28 so as to heat the topsurface 22 of the panel 18.

As a person skilled in the art will readily appreciate, the abovedescription is meant as an illustration of implementation of theprinciples of this invention. This description is not intended to limitthe scope or application of this invention and that the invention issusceptible to modification, variation and change, without departingfrom the spirit of the invention, as defined in the following claims.

1. A foot heating device for a vehicle, the device comprising: a panelhaving a bottom surface for positioning on the floor of the vehicle, thepanel also having a top surface for supporting the feet of an occupantof the vehicle, the panel further including: an insulating layer; aradiant barrier layer disposed adjacent to the insulating layer; and aheating layer disposed between the radiant barrier layer and the topsurface, the heating layer including a heater disposed therein, theheater providing heat for heating the top surface; a lower portion ofthe panel is defined between the heater and the bottom surface of thepanel and has a first thermal resistance, an upper portion of the panelis defined between the heater and the top surface of the panel has asecond thermal resistance, wherein the first thermal resistance isgreater than the second thermal resistance.
 2. The device according toclaim 1 wherein a ratio of the first thermal resistance to the secondthermal resistance is at least about 5:1.
 3. The device according toclaim 1 wherein the panel further includes a decorative layer providedover the heating layer, the decorative layer including the top surface.4. The device according to claim 1 wherein the insulating layer includesthe bottom surface.
 5. The device according to claim 1 wherein theinsulating layer includes a plurality of spaced apart ribs extendingfrom a base layer generally toward the floor of the vehicle.
 6. Thedevice according to claim 1 further comprising an ON-OFF switchelectrically coupled to a power supply of the vehicle and the to theheater to form an electrical circuit.
 7. The device according to claim 6wherein the heater includes electrical resistance heating elements thatprovide heat and the panel further includes one of a thermostat and apositive temperature coefficient device, which is electrically coupledto the electrical circuit and controls the heating portion to within atemperature range.
 8. The device according to claim 6 wherein the heaterincludes positive temperature coefficient thermistor heaters forproviding heat which are self-regulating to within a temperature range.9. The device according to claim 1 wherein the heating layer is in fluidcommunication with an HVAC system of the vehicle and is configured toadvance air received from the HVAC system along the heating portion andto dispense the air directed towards the occupant's feet.
 10. The deviceaccording to claim 9 wherein the heating layer further includes aplurality of channels juxtaposed within the heating layer, the channelshaving each a receiving end that receives the air from the HVAC systemand a dispensing end that dispenses the air.
 11. The device according toclaim 10 wherein the panel further includes a deflector proximate to thedispensing ends and positioned such that the dispensing air is directedtowards the occupant's feet.
 12. The device according to claim 10wherein heating elements are provided within the channels.
 13. Thedevice according to claim 9 further including a duct that provides fluidcommunication between the HVAC system and the heating layer.
 14. Thedevice according to claim 13 further including positive temperaturecoefficient thermistor heaters disposed within the duct, the positivetemperature coefficient thermistor heaters being electrically coupled toa HVAC controller that controls the HVAC system and to a vehicle powersupply to form an electrical circuit such that when cool air from theHVAC system is received within the duct the positive temperaturecoefficient thermistor heaters heat the air and when warm air from theHVAC system is received within the duct the positive temperaturecoefficient thermistor heaters do not substantially heat the air.
 15. Afoot heating device for a vehicle floor, the device comprising: a panelhaving a bottom surface for positioning on the floor of the vehicle, thepanels also including a top surface for supporting the feet of anoccupant of the vehicle, the panel including: an insulating layer; aradiant barrier layer disposed adjacent to the insulating layer; and aheating layer disposed between the radiant barrier layer and the topsurface, the heating layer including a heater comprised of a pluralityof channels with the heating layer, the heating layer being disposedalong the channels and configured to provide heat for heating the topsurface; a lower portion of the panel is defined between the heater andbottom surface of the panel and has a first thermal resistance; and anupper portion of the panel is defined between the heater and the topsurface of the panel and has a second thermal resistance, wherein thefirst thermal resistance is greater than the second thermal resistance.16. The device according to claim 15 wherein the channels are in fluidcommunication with an HVAC system of the vehicle and have a receivingend that receives air from the HVAC system, and a dispensing endconfigured to dispense the air towards the occupant's feet.
 17. Thedevice according to claim 15 further comprising heating elements locatedwithin the channels and an ON-OFF switch that is electrically coupled toa power supply of the vehicle and the heating elements to form anelectrical circuit, the panel further including one of a thermostat anda positive temperature coefficient device, which is electrically coupledto the electrical circuit and controls the heating elements to within atemperature range.
 18. The device according to claim 15 furthercomprising heating elements located within the channels and an ON-OFFswitch that is electrically coupled to a power supply of the vehicle andthe heating elements to form an electrical circuit, the heating elementsincluding positive temperature coefficient thermistor heaters forproviding heat which is self-regulating to within a temperature range.19. The device according to claim 15 wherein a ratio of the firstthermal resistance to the second thermal resistance is at least about5:1.
 20. The device according to claim 15 further including a duct andpositive temperature coefficient thermistor heaters disposed within theduct, the duct providing fluid communication between the HVAC system andthe channels, the positive temperature coefficient thermistor heatersbeing electrically coupled to a HVAC controller that controls the HVACsystem and a vehicle power supply to form an electrical circuit suchthat when cool air from the HVAC system is received within the duct thepositive temperature coefficient thermistor heaters heat the air towithin a temperature range and when warm air from the HVAC system isreceived within the duct the positive temperature coefficient thermistorheaters do not substantially heat the air.